The shelf life of produce or produce materials, including whole plants plant parts thereof including fruits, vegetables, tubers, bulbs, cut flowers and other active respiring plants or plant materials, is typically determined, at least in part, by the amount of an ethylene hormone generated by the respiring plant material. Ethylene is a known plant ripening or maturation hormone. At any substantial concentration of ethylene in and around the plant material, the maturation of the plant is initiated, maintained or accelerated, depending on concentration. See, Burg et al., Plant Physiol. (1967) 42 144-152 and generally Fritz et al. U.S. Pat. No. 3,879,188. Many attempts have been made to either remove ethylene from the ambient package atmosphere surrounding the produce or to remove ethylene from the storage environment in an attempt to increase shelf life. Reduced ethylene concentration is understood to be achieved through a decrease in the stimulus of a specific ethylene receptor in plants. Many compounds other than ethylene interact with this receptor: some mimic the action of ethylene; others prevent ethylene from binding and thereby counteract its action.
Many compounds that act as an antagonist or inhibitor block the action of ethylene by binding to the ethylene binding site. These compounds may be used to counteract ethylene action. Unfortunately, they often diffuse from the binding site over a period of several hours leading to a reduction in inhibition. See E. Sisler and C. Wood, Plant Growth Reg. 7, 181-191 (1988). Therefore, a problem with such compounds is that exposure must be continuous if the effect is to last for more than a few hours. Cyclopentadiene has been shown to be an effective blocking agent for ethylene binding. See E. Sisler et al., Plant Growth Reg. 9, 157-164 (1990). Methods of combating the ethylene response in plants with diazocyclopentadiene and derivatives thereof are disclosed in U.S. Pat. No. 5,100,462 to Sisler et al. U.S. Pat. No. 5,518,988 to Sisler et al. describes the use of cyclopropenes having a C1-4 alkyl group to block the action of ethylene.
A preferred olefinic antagonist or inhibitor of receptor sites or ethylene generation in produce is 1-methylcyclopropene, derivatives and analogs thereof have also been tried as an antagonist or inhibitor for the generation of ethylene from respiring plant or produce material. 1-methyl-cyclopropene (1-MCP), 1-butene and other olefins have been shown to have at least some measurable activity for inhibiting ethylene generation and thus extending shelf life. We find that 1-butane is a good model for 1-MCP activity A number of proposals have been made for the method of producing and releasing 1-MCP to inhibit ethylene release and as a result slowing maturation and maintaining the quality of plant materials. Currently 1-MCP is dispensed directly from a pressure vessel or by the release of 1-MCP from a sachet containing complexed 1-MCP. In these technologies, 1-MCP is released from a point source which causes a concentration of gradient within the storage chamber thus resulting in a variation in maturation inhibition wherein some produce has an extended life time where other produce exposed to a lesser concentration 1-MCP tends to have less inhibition of ethylene and has a reduced shelf life.
Notwithstanding these efforts, there remains a substantial need in the art for improved plant maturation and degradation prevention.